Add usage examples documentation

EXAMPLES.md

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+# Usage Examples
+
+## Example 1: Creating a certificate for a new server (Interactive)
+
+```bash
+./cert-manager.py
+```
+
+**Session output:**
+```
+============================================================
+Interactive Certificate Manager
+============================================================
+
+--- Certificate Details ---
+Target Host (IP or hostname): 192.168.1.50
+Common Name (FQDN): webserver.egonetix.lan
+
+--- Certificate Subject (press Enter to use defaults) ---
+Country (C) [DE]: 
+State/Province (ST) [berlin]: 
+Locality (L) [berlin]: 
+Organization (O) [egonetix]: 
+Organizational Unit (OU) [it]: 
+Validity (days) [3650]: 
+
+============================================================
+Summary:
+============================================================
+Target Host:     192.168.1.50
+Common Name:     webserver.egonetix.lan
+Country:         DE
+State:           berlin
+Locality:        berlin
+Organization:    egonetix
+Org Unit:        it
+Validity:        3650 days
+CA Server:       10.0.0.21
+Output files:    webserver.req, webserver-cert.pem
+============================================================
+
+Proceed with certificate generation? [Y/n]: y
+
+============================================================
+Step 1: Generating CSR on target host
+============================================================
+[Generates CSR on 192.168.1.50...]
+
+============================================================
+Step 2: Signing certificate with CA
+============================================================
+[Signs certificate with UCS CA...]
+
+============================================================
+Step 3: Deploying certificate to target host
+============================================================
+Do you want to copy the certificate back to the target host? [Y/n]: y
+
+✓ Certificate copied to target host at /tmp/webserver.crt
+  Private key is at /tmp/webserver.key
+
+============================================================
+✓ Certificate Management Complete!
+============================================================
+
+Files created:
+  - webserver.req (Certificate Request)
+  - webserver-cert.pem (Signed Certificate)
+
+On target host (192.168.1.50):
+  - /tmp/webserver.key (Private Key)
+  - /tmp/webserver.crt (Certificate)
+```
+
+## Example 2: Using standalone scripts
+
+### Generate CSR only:
+```bash
+./generate-csr.sh 10.0.0.1 gwnue01.egonetix.lan
+```
+
+### Sign existing CSR:
+```bash
+./sign-cert.sh gwnue01.req gwnue01 3650
+```
+
+## Example 3: Changing default values
+
+First run with modified defaults:
+```bash
+./cert-manager.py
+```
+
+Answer "y" to "Do you want to modify default values?"
+
+Set your new defaults (e.g., different organization, longer validity period).
+
+These defaults are saved in `~/.cert-manager-config.json` and will be used for all future runs.
+
+## Example 4: Batch processing
+
+For multiple certificates, create a wrapper script:
+
+```bash
+#!/bin/bash
+# batch-certs.sh
+
+hosts=(
+  "10.0.0.1:gwnue01.egonetix.lan"
+  "10.0.0.10:nas.egonetix.lan"
+  "10.0.0.20:monitoring.egonetix.lan"
+)
+
+for entry in "${hosts[@]}"; do
+  host="${entry%%:*}"
+  fqdn="${entry##*:}"
+  
+  echo "Processing $fqdn on $host..."
+  ./generate-csr.sh "$host" "$fqdn" DE berlin berlin egonetix it
+  
+  shortname=$(echo "$fqdn" | cut -d'.' -f1)
+  ./sign-cert.sh "${shortname}.req" "$shortname" 3650
+  
+  echo "Done with $fqdn"
+  echo ""
+done
+```
+
+## Tips
+
+1. **First run:** Use the interactive tool to set up your defaults
+2. **Repeated certificates:** The tool remembers your last target/common name
+3. **Different organizations:** Modify defaults when needed for specific use cases
+4. **Automation:** Use the standalone scripts for scripting/automation
+5. **Verification:** Always check the certificate details after generation